Background of the Invention
Field of Invention
[0001] In the printing industry, and particularly in a printing process, a continuous web
of paper is first passed through the printing press which makes the ink impressions
on the web. The moving web is then immediately passed through an oven to remove solvents
and wetting solution retained from the printing process. The web is then cooled down
by passing it over chill rollers. At this point the web is then ready to be folded
and cut into its final format.
[0002] The present invention relates to an improved system for cutting a continuous paper
web into separate sheets or signatures, alternately diverting or separating the individual
sheets into two paths to create a space or gap between successive sheets and then
decelerating and shingling or overlapping the successive sheets for delivery of the
sheets to a subsequent process such as a sheet counter or stacker system as described
in my pending application serial number 704,676. The present invention operates equally
well with signatures which are one sheet thick or with signatures which are several
sheets thick such as pamphlets, magazines or newspapers.
[0003] It is desirable to provide a diverter and delivery system in which sheets cut from
the continuous web are alternately diverted into separate delivery paths by an improved
diverter means. Additionally, it is desirable to provide an improved diverter and
delivery system which maintains continuous, positive control over the sheets while
the sheets are first cut and alternately diverted and then shingled in preparation
for delivery to a subsequent processing station. Moreover, it is desirable to provide
an improved delivery system which operates at a dramatically increased speed with
respect to present delivery systems. The cutting operation, described in connection
with the preferred embodiment of the present invention, is fully set forth in and
described in my U.S. Patent No. 4,426,897.
[0004] Previous diverting systems employ various methods and devices for directing sheets.
The prior art discloses fixed or static diverters; cutting cylinders which additionally
function as diverters; and rotating cam diverters.
[0005] Fixed or static diverters are disposed across the paper path and these diverters
operate by having the sheets physically strike the diverter. The momentum of the moving_sheets
and the shape of the diverter surface combine to channel the sheets to the appropriate
delivery conveyor. Such fixed diverter systems create the possibility of a lead edge
foul condition as the lead edge of each sheet hits the diverter; generate static in
the sheets as the sheets move across the stationary surface of the diverter; and are
not variable in width to adapt to paper of differing widths. Each of these problems
can ultimately jam the system thereby losing valuable time while the jam is cleared,
wasting large amounts of paper in getting the system back up to running speed, and
potentially damaging the machine itself. Lead edge foul is even more probable with
a signature of more than one sheet when the leading edge is open. Due to the speed
of travel of the signature, the leading edges of the group of sheets may separate
thereby presenting a ripe target for causing a jam with the forward edge of the fixed
diverter.
[0006] The problems associated with static diverters multiply when single sheets or signatures
comprised of a few lightweight sheets are involved rather than a folded signature.
Single or thin bundles of sheets, when unfolded, have less structural rigidity and
are more apt to buckle when striking the fixed diverter. With folded signatures, a
rigid spine is created by the fold which aids in maintaining structural integrity
of the sheets as they strike and slide across the diverter. Moreover, the static generated
from sheets sliding across the surface of the diverter is more likely to stop or misalign
a single sheet of paper, because of its lighter weight, than a bundle of sheets.
[0007] In other prior art systems the cutting operation can perform the dual function of
cutting the web of paper and then alternately diverting the individual sheets. In
such systems, the web is passed between two, opposed knife cylinders, each of which
includes a knife edge that is 180° out of phase with the knife edge of the other cylinder.
These knife cylinders further include a row of cam operated pins which pierce and
grip the web and then deliver the cut sheet to an associated delivery cylinder. Each
delivery cylinder includes a cam operated gripper that grabs the leading edge of the
cut sheet as the pins in the knife cylinder are withdrawn and deposits the cut sheets
in a shingled fashion on a delivery conveyor system. As each successive sheet is layed
down in a shingled format on the respective delivery conveyors, the gripper of the
delivery cylinder releases the sheet. However, operations such as these create a great
deal of wasted paper because the sheet edges must be subsequently cut in order to
remove the pin holes. Moreover, the need to cut the edges adds a further processing
step to the overall system which increases the time to produce a finished product
and increases the costs.
[0008] Still further prior art systems disclose rotary cam diverters for alternately diverting
successive sheets between two delivery systems. An example is shown in the British
Patent 1,208,969. However, the system disclosed therein, because of its construction,
creates potential jamming problems. Specifically, as the lower cams divert a sheet
to the upper delivery system, the placement of the cams combined with the physical
contour of the cams cause the cams to lose contact with the leading edge of the sheet
prior to the sheet becoming trapped between the opposed belts of the upper delivery
system. This lack of support can cause the leading edge of the sheet to drop and miss
the entry into the delivery system. As a result, the sheet would foul and jam the
system. Additionally, the static associated with the overlying belt against which
the cams trap the sheet would actually repel a single or lightweight sheet prior to
the leading edge being engaged by the upper and lower opposed belts of the delivery
system. Consequently, the same fouling or jamming would occur.
[0009] In an attempt to remedy these problems, the prior art further shows the addition
of guide members or steeples, as are shown in U.S. Patent 4,373,713, which act in
combination with the cams to provide continued support for the sheets while they are
diverted to the delivery conveyors. While solving the support problem these guide
plates create still greater static problems. As with a fixed diverter, the sheets
are required to slide across the guide member which action creates static electricity.
The generated static is sufficient to impede and misalign, if not jam, single or lightweight
sheets. Consequently, the system disclosed is not only limited in the number, type
and weight of sheets it can run but, more importantly, the system creates additional
problems which it does not solve.
[0010] Various delivery systems, for shingling sheets are also set forth in the prior art.
With delivery systems generally, it has always been a goal to increase the overall
operating speed of the system. While printing presses operate at high speeds, it has
always been necessary to drastically reduce the speed of the sheets in the delivery
system both to shingle and to square the sheets. Squaring the sheets may be achieved
by allowing the lead edge of each sheet to strike a fixed object such as a squaring
roller. However, to avoid permanent damage to the sheets, particularly single or lightweight
sheets, the paper should not be travelling faster than about 300 feet per minute.
This limitation is a physical characteristic of most normal weight paper and, consequently,
limits the overall output of the printing system by necessitating a reduced operating
speed for the delivery system.
[0011] One delivery means known in the art is described above in connection with the rotary
knife cylinders and cam operated pin grippers. This system employs a pair of delivery
cylinders which grip alternate sheets and deposit them in overlapping relation on
separate delivery conveyors. However, the need to cut off the edges of the sheets
to remove the pin holes creates an additional handling step which makes this system
slow and inefficient.
[0012] Another prior art delivery system employs a fan like element to shingle the sheets.
By means of gravity, sheets are caused to fall into a receptive slot in a rotating
fan-like delivery means. As the delivery means rotates the sheets fall out one after
the other in an overlying or shingled arrangement. However, once a sheet has entered
the fan delivery, the timing of the entire delivery system is subject to the gravitational
forces working on the sheet. As a result, lightweight sheets could severely slow down
a system otherwise capable of operating at higher speeds. The delivery system of the
present invention improves upon this arrangement by maintaining continuous and positive
control of each and every sheet, which this prior art system cannot do, and by increasing
the operating speed with respect to this prior art system.
[0013] Other prior art delivery systems employ rotary knock down arms for decelerating the
sheets but still require squaring rollers for aligning the sheets. While the knock
down arms, by acting on the tail of the sheets, are an improvement over the use of
fixed stops in decelerating the sheets, critical speed limitations are still present
because of the squaring roller. Moreover, the knock down arm merely strikes the rapidly
moving sheet throwing the sheet against a lower, slow speed belt. Because the sheet
is unrestrained at this time the chance of it becoming misaligned or out of square
is great.
[0014] An improvement over that system is disclosed in my U.S. Patent 3,994,221. While still
using a squaring roller, the deceleration procedure is improved by the use of a series
of freely rotating snubber wheels mounted on rotating snubber support plates. Instead
of only knocking the sheet down, allowing it to bounce onto the lower, slow speed
belt, the snubber wheels actually physically trap the tails of the sheets against
the slow speed belt while the lead edges of the sheets engage the squaring roller.
This causes the sheets to decelerate more quickly but can still cause a misalignment.
Consequently a squaring roller is still needed and still places a speed limitation
on the system.
[0015] The present invention overcomes all of the aforementioned problems by maintaining
a positive control over the sheets exiting the opposed, high-speed belts, during the
decelerating process of the snubbers and during subsequent delivery. Specifically,
the snubber wheels trap the individual sheets against the lower, slow speed belts
while the tail of the sheets are still engaged by the opposed high-speed belts or
immediately after the sheet has left the high-speed belts. While this may create a
slight overfeed of the tail end of the sheets, it is not significant enough to permanently
crease the sheets. By maintaining this positive control, the sheets are never allowed
to become unaligned. Thus, the continual positive control allows the removal of the
squaring roller which, in turn, allows the system to operate at a faster speed.
OBJECTS OF THE INVENTION
[0016] It is a general object of this invention to provide an improved sheet cutting, diverting
and delivery system for use in connection with printing processes which positively
controls each sheet throughout the entire process.
[0017] It is a further object of this invention to provide an improved diverter for separating
a continuous stream of sheets into two paths.
[0018] It is another object of this invention to provide an improved means for delivering
the sheets in a shingled or overlapped format.
[0019] It is still another object of the invention to provide an improved delivery system
which does not require squaring rollers or similar fixed squaring means.
SUMMARY OF THE INVENTION
[0020] In accordance with one embodiment, a continuous web of paper is caused to travel
by a first conveyor at a constant, high speed. The web is engaged by a pair of opposed
nip rollers which maintain the alignment of the web. The web then passes between a
rotary knife cylinder, with four blades, and an opposed anvil cylinder which cuts
four equal length sheets or signatures from the web for every revolution of the knife
cylinder. However, before each successive sheet is cut from the web, the leading edge
of the web, defined by the stroke of the previous blade, engages a pair of opposed
nip rollers arranged downstream of the cutter. These nip rollers rotate at an angular
velocity which is approximately eight percent faster than the speed of the web. Consequently,
the nip rollers ensure that the leading edge of the next successive sheet to be cut
from the web is held positively and securely in place and the acceleration experienced
by the lead edge of the web insures that the web is under tension while the next sheet
is cut away from the web. These features prevent jamming of the system which occurs
in present systems where the sheets are unrestrained, allowing them to become easily
unaligned.
[0021] In order to then shingle the sheets for delivery to a subsequent operation, such
as counting and stacking, it is necessary to create a gap or space between the successive
sheets. At this point, the trailing edge of each sheet cut from the web is followed
directly by the leading edge of the next sheet. While a space is created between sheets
due to the eight percent increase in speed of the nip rollers, this space is insufficient
to allow proper shingling of the sheets. One way to cause the formation of a sufficient
gap is to alternately divert each successive sheet between two separate delivery systems.
This will create a space between successive sheets at least equal to the length of
an individual sheet and will be sufficient to allow the delivery portion of the present
invention to decelerate and shingle the sheets as desired.
[0022] In addition to positively securing the sheets during cutting, the pair of nip rollers
following the cutting cylinder define the entrance to the two delivery systems. The
upper nip roller is part of a second conveyor system which comprises an upper delivery
section. The lower nip roller is part of a third conveyor system which comprises a
lower delivery section. Of course, the two delivery systems will function just as
well in any relative orientation. As the successive sheets pass through the forward
nip rollers they then encounter the sheet diverter of the present invention. The sheet
diverter, as the name implies, diverts the sheets from their original path into either
the upper delivery section or the lower delivery section. The sheet diverter includes
two sets of multiple diverting cams which rotate in opposite directions about a pair
of cam shafts. In operation, each set of rotating diverter cams are synchronized to
alternately engage the successive sheets being fed from the cutting cylinder and divert
the sheets to either the upper delivery section or the lower delivery section.
[0023] More specifically, the lower set of rotary cams engage a sheet and, through their
rotation, divert the sheet upwardly where the top surface of the sheet engages a series
of upper, high speed conveyor belts. These high speed conveyor belts are part of the
upper delivery section and traiiverse the upper nip roller. As the sheet continues
into the upper delivery section, the surface of the diverter cam remains in underlying
contact with the sheet, guiding the sheet between the surface of the cam and the upper
high-speed belts until the lead edge of the sheet passes over an idler roller comprising
the beginning of an underlying high-speed conveyor. At this point, the leading edge
of the sheet is now trapped between the upper high-speed belts and the underlying
high-speed belts and the cams are still positively guiding the remainder of the sheet
against the upper belts. The opposed high-speed belts transport the sheet to the shingling
section of the upper delivery section.
[0024] It is an important feature of the present invention that the cams engage and support
the entire sheet, including most importantly, the leading edge, up until the leading
edge is engaged by the opposed high-speed belts of the delivery section. This guarantees
positive control of the sheets during the entire diverting process and prevents the
problems associated with the prior art devices. Particularly, the generation of static
is prevented because the sheets do not have to slide over any fixed or stationary
objects. Instead, the cams rotate at approximately the same speed as the overlying
high speed conveyor belts. As the cams continue their rotation, the tail of the sheet
is disengaged and the cams and the entire sheet is now disposed between the opposed
high-speed belts. The cams then complete their revolution and engage another sheet.
[0025] The diverting of sheets to the lower delivery section operates in much the same manner.
Due to the synchronized movement of the rotary cams, after the lower diverter cams
have completed diverting a sheet into the upper delivery section, the upper diverter
cams are in position to divert the next subsequent sheet into the lower delivery section.
In this instance, however, the surface of the upper cams divert the sheet downwardly
and trap the lower surface of the sheet against a series of high-speed belts comprising
part of the lower delivery section. During completion of the revolution of the upper
diverter cams the sheet passes beneath a series of overlying high-speed belts which,
in conjunction with the underlying high-speed belts, trap the sheet and transport
it to the shingling portion of the lower delivery system. As with diverting sheets
to the upper delivery section, the sheets are subject to continuous positive control.
[0026] As is readily apparent, the synchronized rotating cams operate to alternately divert
sheets cut from the web without the use of cam controlled pins or grippers. Furthermore,
the rotating cams are an improvement over prior art fixed diverters which lie in the
path of the incoming sheets. Fixed diverters, such as these, are pointed toward incoming
sheets, and cause fouling or jamming of the system when the leading edge of an incoming
sheet hits the leading edge of the fixed diverter. Additionally, the static build
up associated with sheets passing over stationary surfaces is avoided by the present
invention. The diverter cams rotate at an angular velocity corresponding to the speed
of the sheets and, therefore, the sheets do not slide over any stationary surface.
[0027] Once trapped between the two sets of high-speed belts, the upper and lower delivery
sections are the same. Because the sheets are subject to the same operations, only
one delivery section will be described. The delivery sections decelerate and shingle
the sheets so that they are in a format for delivery to a counter and stacker operation.
A similar delivery system is described in my ; pending application serial number 768,897,
however, the delivery sections of the present invention contain important differences
and improvements which will become apparent upon comparison.
[0028] In operation of either the upper or lower delivery section, the sheets are fed into
the deceleration and shingling portion at high speed by opposed, face to face, high-speed
conveyor belts. The lower, high-speed conveyor belt ends short of the deceleration
and shingling portion. A low-speed conveyor belt begins just downstream of the terminating
end of the lower, high-speed conveyor belt and is dropped relative to the plane of
the latter. Also, the continuing upper, high-speed belts as well as the lower, low-speed
belts are slightly declined at a downward angle of approximately three degrees. This
ensures that the sheets exiting between the opposed, high-speed belts maintain contact
with the continuing upper, high-speed belts.
[0029] As the leading edge of the sheet emerges from between the opposed, high-speed belts
a series of dual snubber wheels freely mounted on rotating snubber support plates,
timed with the rotation of the knife cylinder, strip the leading edge of the sheets
off the upper high-speed belts. As the sheets continue their forward travel one set
of the dual snubber wheels drives the sheets downwardly and against the low-speed
belts. Because the sheets are continuing their forward movement the snubbers actually
trap the tail end of each sheet against the low speed belt. However, the physical
trapping of the sheets between the snubbers and the low-speed belts, resulting in
the necessary deceleration of the sheet for shingling, occurs while the tail edge
of the sheet is still held between the opposed, high-speed belts or just following
the departure of the sheet therefrom. By decelerating the sheets in this manner, not
only are the sheets always subject to positive control, thus avoiding the sheets from
becoming out of alignment and creating a jam or foul, but the invention prevents damage
to the sheets. Perhaps more importantly, because the sheets are maintained in alignment,
there is no need for a squaring roller. Without a squaring roller, the system can
be operated at speeds well in excess of 300 feet per minute.
[0030] The preferred embodiment employs dual snubber wheels, 180 degrees apart, rather than
single snubber wheels, to provide longer contact with the sheets, thereby allowing
greater control and positive deceleration. The snubbers rotate at a one to one ratio
with the knife cylinder which cuts four sheets for every single rotation and the snubbers.
However, because the sheets are alternately diverted between the upper and lower delivery
sections, a gap exists between the sheets and the snubbers must only decelerate two
sheets per revolution. Having two snubber wheels 180 degrees apart, the snubber wheels
can maintain longer contact with the individual sheets than if the snubber had only
one wheel. A single wheel snubber would have to rotate at twice the speed in order
to match the output of the knife cylinder. Moreover, if there was no gap between the
sheets, but instead, one sheet was immediately behind the next sheet, the time for
deceleration would be drastically reduced. As a result, more snubbers would have to
be added. The three snubbers of the preferred embodiment of the present invention
would not be able to sufficiently slow the sheets if the deceleration time was reduced.
Consequently, a more efficient system is achieved by the present invention by alternately
diverting the sheets prior to deceleration and, thereby, using fewer snubbers to achieve
the desired deceleration.
[0031] As the sheets are decelerated and laid flat against the low-speed belts, the snubber
wheels continue their rotation in the direction of sheet travel and lift off the surface
of the sheet just as the leading edge of the next sheet is emerging from between the
opposed high-speed belts. At this point, the second set of snubber wheels engage the
lead edge of this sheet and decelerate the sheet in the same manner as previously
described. However, the previous sheet, traveling at a slower speed, is overlapped
by this next succeeding sheet thereby achieving the desired shingling of the sheets.
The specific length of the shingle or overlap is readily adjustable by changing the
speed of the lower, low-speed belt. Additionally, downstream of the dual snubber wheels,
it is desirable to have a plurality of controlling rollers positioned to trap the
leading edge of each succeeding sheet. The controlling rollers should be positioned
so that the leading edge of each sheet is engaged before the next subsequent sheet
is decelerated against it by the snubbers. This will prevent the underlying sheets
from becoming misaligned and jamming the system. Once in a shingled or overlapped
format, the sheets are delivered to the next process such as counting and stacking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] To provide for a more complete understanding of this invention, a preferred embodiment
of the invention is illustrated in greater detail in the accompanying drawings.
[0033]
Figure 1 is a perspective view of the sheet diverter and delivery system with much
of the structure removed for clarity.
Figure 2 is a cross sectional view of the primary elements of the sheet diverter and
delivery system.
Figure 3 is a diagrammatic elevational view of the sheet diverter and delivery system
showing a portion of the gear drive.
Figure 4 is a cross-sectional and partial cutaway view of the sheet diverter and delivery
system taken about line 4-4 of Figure 2.
Figure 5 is a cross-sectional view of a safety clutch system that may be used with
the present invention.
Figures 6, 7 and 8 illustrate in greater detail the operation of the sheet snubber
assemblies of the present invention.
DETAILED DESCRIPTION
[0034] The following detailed description will permit a more complete understanding of this
invention. However, the embodiment described below is simply an example of the invention
and the invention is not limited to this embodiment. Furthermore, the drawings are
not necessarily to scale and certain elements may be illustrated by graphic symbols
and fragmentary views. In certain instances, details may have been omitted which are
not necessary for an understanding of the present invention, including conventional
details of fabrication and assembly.
[0035] Generally, the present invention relates to a system for cutting a continuous paper
web into separate sheets or signatures, alternately diverting the individual sheets
to one of two paths, thereby creating a space or gap between successive sheets, and
then decelerating and shingling the successive sheets for delivery to a subsequent
process. The device of this invention is intended to be integrated into a full service
printing system, and will supply shingled sheets of printed material to a subsequent
processing station such as a counting and stacking operation.
[0036] Turning to the drawings, Fig. 1 shows a perspective view of the sheet diverting and
delivery system 10 of the present invention. Much of the frame structure is not shown
to more clearly illustrate the belt, roller and cam configurations of the diverter
and delivery sections.
[0037] A continuous web of paper 11 is drawn into the sheet diverting and delivery system
10 between opposed nip rollers 13 and 15 at a speed of approximately 2000 feet per
minute. The leading edge of the web passes between the anvil cylinder 17 and the rotary
knife cylinder 19 and engages a second pair of opposed nip rollers 21 and 23. These
nip rollers 21 and 23 rotate at a velocity approximately eight percent faster than
the speed of the incoming web 11, and the resulting acceleration of the lead edge
of the web creates tension in that portion of the web between the first set of nip
rollers 13 and 15 and the opposed nip rollers 21 and 23 passing between the anvil
cylinder 17 and rotary knife cylinder 19. As the web is held firmly in place and under
tension as a result of the action of these nip rollers 21 and 23, one of the four
blades 25 of the rotary knife cylinder 19 rotates into position and cuts a sheet from
the web 11.
[0038] In the preferred embodiment the blades 25 are straight but it is also possible to
use serrated blades. In such a case, however, the anvil surface would need to be constructed
of some type of resilient material such as urethane or the anvil would need slots
for the tips of the serrated blades to recess during cutting.
[0039] As shown in Fig. 4, the anvil cylinder 17 is rotatably mounted to the frame 12 by
means of an axle 29 housed within appropriate bearings as is well known in the art.
Power is supplied to the anvil cylinder 17, and consequently to the rest of the diverter
and delivery system, from a printing press (not shown) through the drive gear 31 engaging
the main drive gear 33 on the anvil cylinder axle 29 as shown in Figs. 3 and 4. By
being directly driven by the printing press, proper timing between the respective
sections of the entire operation is assured.
[0040] The nip rollers 13 and 15 are rotatably mounted to the frame 12 by means of axles
housed within appropriate bearings (not shown). These nip rollers 13 and 15 each have
a corresponding drive gear 14 and 16, respectively (Fig. 3), mounted on the axle about
which the nip rollers rotate. The infeed nip roller gear 16 is in contact with, and
is driven by the interconnecting drive gear 27 which, in turn, is in contact with
and is driven by the main drive gear 33 fixably mounted on the axle 29 of the anvil
cylinder 17. The interaction between the nip roller gear 14 and the nip roller gear
16 causes the nip roller 13 to rotate.
[0041] By changing the size of the lower nip roller 15, the speed of paper feed can be adjusted
and, therefore, the length of sheets cut from the web easily adjusted. For example,
making the lower nip roller 15 smaller will cause the web speed to decrease. Consequently,
the sheets cut by the knife cylinder 19 will be shorter. The converse is true if the
nip roller 15 is made of larger diameter. Additionally, to allow this adjustability,
it will be necessary to place the axles of both the lower nip roller 15 and the interconnecting
drive gear 27 on eccentrics to allow for vertical adjustment in accommodating any
changes in size of the roller.
[0042] The rotary knife cylinder 19 is rotatably mounted to the frame 12 by means of the
knife cylinder axle and bearing assembly (not shown) disposed in overlying relation
to the anvil cylinder 17. The four knife blades 25 are affixed to the rotary knife
cylinder 19, by commonly known means at 90° intervals, as shown in Fig. 2. The rotary
knife cylinder 19 and the anvil cylinder 17 are positioned so that the cutting edge
of each blade 25 will just contact the anvil cylinder at the lowest point in the rotation
path of the blade 25. Of course, the vertical position of the rotary knife cylinder
19 and the cutting blades 25 may be adjusted to accommodate signatures or sheets of
varying thicknesses.
[0043] As also shown in Fig. 4, the drive shaft 35 supplies power to the diverter and delivery
sections of the present intention through the main drive gear 33 driving a bevel gear
34 mounted on the anvil cylinder axle 29, which bevel gear 34 drives receptive bevel
gear 36 mounted on the drive shaft 35. The main drive gear 33 drives the rotary knife
cylinder 19 by means of a knife cylinder gear 37, shown in Fig. 3, mounted on the
rotary knife cylinder axle (not shown). The size of the anvil cylinder 17 and the
knife cylinder 19 as well as the respective drive gears 33 and 37 are appropriately
selected so that the knife cylinder 19 and anvil cylinder 17 rotate at a ratio of
1 to 1.
[0044] After the sheet is cut from the web 11, it continues to be drawn into the nip of
the opposed nip rollers 21 and 23 until it contacts either the rotating upper diverter
cams 39, 41 and 43 or the lower diverting cams 45, 47 and 49. As is best seen in Fig.
1, the rotating diverting cams are positioned and synchronized so that sheets are
alternatively directed toward either the upper delivery system 50 or the lower delivery
system 52. The upper nip roller 21 is a part of the conveyor system defined by a pair
of upper, high-speed belts 51, while the lower nip roller 23 is a part of the conveyor
system defined by belts 53. In the preferred embodiment of the present invention the
nip rollers 21 and 23 are rotating at a surface velocity approximately eight percent
greater than the speed of the web 11. Consequently, each successive sheet experiences
a slight acceleration as it is cut from the web.
[0045] Line 4-4 of Fig. 2 defines the center line of the system. The function and structure
of the components above line 4-4 is largely the same as that below the line. A top
view of the lower structure is shown in greater detail in Fig. 4 and will be described
in detail below.
[0046] As seen in Fig. 4, the main drive gear 33 engages gear 55 mounted on the end of axle
57. Axle 57, in turn, supplies rotational power to the drive roller 59. The drive
roller 59 is in contact with the pair of friction belts 53, Fig. 2, which belts 53
constitute the lower, high-speed conveyor system of the lower diverter and delivery
sections of the invention. The belts 53 also traverse the nip roller 23 and the idler
rollers 61 and 63. Preferably, the ratio between the main drive gear 33 and gear 55
is such that drive roller 59 drives the lower, high-speed belts 53 at a speed approximately
eight percent faster then the speed of the incoming continuous web 11 of paper.
[0047] The drive roller gear 55, in turn, drives the lower camshaft gear 65 mounted on the
lower camshaft axle 67 of the lower diverter cam shaft 69 which is rotatably mounted
in the frame 12 in appropriate bearing means. The lower diverting cams 45, 47 and
49 are rigidly mounted on the lower camshaft 69.
[0048] As shown in Figs. 1 and 2, an upper diverting system similar to the lower diverting
system just described is disposed above the lower diverting system. This upper diverting
system employes a set of upper diverting cams 39, 41, 43 mounted on an upper camshaft
71 which is mounted in the frame 12 in the same manner as the lower camshaft 69. As
seen in Figs. 2 and 3, the upper camshaft 71 is directly driven by the lower camshaft
69 through the engagement of the upper camshaft gear 73, mounted on the upper camshaft
71, and the lower camshaft gear 65 mounted on the lower camshaft 69. Thus, the upper
and lower camshafts 71 and 69 rotate at the same speed, but in opposite directions.
Furthermore, the upper and lower rotating diverter cams are positioned and synchronized
so as to alternately engage the successive sheets continuously cut from the web and
entering the diverter section of the present invention. Necessarily, the configuration
of driving gears between the anvil cylinder 17 and the camshafts is such that the
camshafts complete two revolutions to every single revolution of the knife cylinder
19 and the anvil cylinder 17.
[0049] A sheet destined for the lower delivery system will pass between the pair of opposed
front nip rollers 21 and 23 and will be positively controlled therebetween until the
upper rotating diverter cams 39, 41 and 43 contact the sheet and guide it against
the pair of lower, high-speed belts 53. As the sheet continues into the lower delivery
system between diverter cams 39, 41 and 43 and belts 53, the leading edge of the sheet
enters the nip created between the opposed upper, high-speed belts 75 and the lower,
high-speed belts 53 before the trailing edge exits the grasp of the opposing nip rollers
21 and 23. Moreover, the surface shape of the cams ensures that the entire length
of each sheet is supported between the opposed nip rollers 21 and 23 and the opposed,
high-speed belts 53 and 75. This further ensures continued positive control of the
sheets during this same length of travel. The sheet is released by the diverter cams
39, 41 and 43 only after the sheet has been positively engaged between the opposed
belts 53 and 75, and the sheet thereafter continues to proceed between these belts
toward the lower delivery section 52.
[0050] The upper, high-speed belts 75 traverse a series of idler rollers 77, 79, 80, 81
and 82 and a drive roller 83. The drive roller 83 drives these belts 75 by frictional
engagement. A bevel gear 85 mounted on the drive shaft 35 supplies rotary power to
the drive roller 83 through the combination of the receptive bevel gear 87 the transfer
gear 89 and the drive roller gear 91. Both the receptive bevel gear 87 and the transfer
gear 89 are mounted on an axle 93 which axle is rotatably mounted in the frame 12
in appropriate bearing means. The transfer gear 89 drives the drive roller gear 91
which is fixed on the drive roller axle 95 of the drive roller 83. The drive roller
83 rotates about the drive roller axle 95 which axle 95 rotates in the frame 12 in
an appropriate bearing means.
[0051] Once a sheet has been diverted into the lower delivery system by the upper diverter
cams 39, 41 and 43 the lower diverter cams 45, 47 and 49 rotate into position to guide
the next succeeding sheet exiting the opposed nip rollers 15 and 17. This next sheet
will be positively guided and supported by diverting cams 45, 47 and 49 against the
upper, high-speed belts 51 until the sheet has totally passed between opposed upper,
high-speed belts 51 and lower, high-speed belts 97. Thus, the continuous stream of
cut sheets is alternately delivered between the upper delivery section and the lower
delivery section. By alternately diverting each sheet in this manner, every sheet
is separated from the next sheet by a distance greater to the length of a sheet. This
gap allows the delivery sections to function.
[0052] As further seen in Fig. 4, the initial idler rollers 77 are rotatably mounted on
the plates 99. These plates 99 are, in turn, mounted on the shafts 101 affixed to
the frame 12. The idler rollers 103 of the upper diverter system are similarly attached
to the plates 99. In order to accommodate sheets of varying widths, these plates 99,
and consequently, the idler rollers 77 and 103 are laterally adjustable along the
shafts 101. Similarly, the upper and lower diverting cams are laterally adjustable
along the respective camshafts and the upper and lower, high-speed belts are laterally
adjustable as well. The lateral adjustability is desirous in order that the edges
of the individual sheets are always supported to thereby avoid the edges becoming
torn or possibly jamming the system.
[0053] As a safety feature, in the preferred embodiment, the diverters also act as jam detectors.
Each camshaft 69 and 71 may be provided with a clutch assembly to allow the camshaft
axle as well as the supporting gears to continue rotating if the sheets should jam
and stop the movement of the diverter cams. As best can be seen in Fig. 5, in connection
with the lower camshaft but equally applicable to the upper camshaft, the lower camshaft
gear 65 which drives the lower camshaft 69 may contain a clutch assembly 105. The
clutch assembly 105 comprises a ball bearing 107 which is forced into a detent 109
in the axle bushing 110 by the spring biased member 111. The spring biased member
111 is, in turn, connected to a clutch plate 113 at its distal end, which clutch plate,
when extended outwardly, trips a system shutdown switch 115. In operation, the camshaft
gear 65 rotates the camshaft 69 by means of the ball bearing 107 positioned in the
detent 109. Should the paper jam and the diverter cams stop rotating, the axle bushing
110 will also stop. However, instead of stripping the gears, the ball bearing 107
will be forced out of the detent 109 pushing the clutch plate 113 out and activating
the system shutdown switch 115. The switch shuts down the printing press and also
activates two pneumatic cylinders operatively connected to the axle of the nip roller
13 thereby lifting the eccentrically mounted upper nip roller 13 off of the web of
paper. This action immediately stops the flow of paper into the diverting section
thereby preventing damage to the machine. Additionally, because the gear 65 is no
longer connected to the axle bushing 110, the gear can continue to rotate while the
system loses its momentum and finally stops as a result of the printing press being
shut down.
[0054] A sheet exiting either the outgoing nip of the high speed belts 51 and 97 at the
drive roller 117 of the upper conveyor system, or the nip of the high-speed belts
53 and 75 at the idler roller 61 of the lower conveyor system, tends to adhere to
the lower surface of the continuing upper belts 51 and 75, respectively, because each
of these upper, high-speed belts are declined at an angle of approximately three degrees
rather than being parallel to the ground. Disposed below the upper, high-speed belts
51 and 75 and adjacent to, but on a lower plane than, the respective lower, high-speed
belts 97 and 53, are the upper and lower, low-speed delivery conveyor systems 50 and
52 defined by the low-speed belts 119 and 121, respectively. These lower, low-speed
belts are also declined at approximately three degrees. This slight downward decline
ensures that the sheets will adhere to the upper, high-speed belts so that the next
subsequent sheet does not collide with the tail of the previous decelerated sheet
which may have dropped into its path otherwise.
[0055] In the lower delivery section 52, the sheets emerge from between the opposed, high-speed
belts 53 and 75 where they are promptly decelerated and shingled for delivery to a
subsequent handling process. The pair of lower, low-speed belts 121 move at a speed
approximately one-sixth or one-seventh the speed of the belts 53 and 75. The sheets
are decelerated by means of a pair of snubber assemblies 123 comprised of a pair of
snubber wheels 125 and 127 freely rotatable on the snubber support plates 129. The
snubber support plates 129 are mounted to a snubber shaft 131 which is driven at a
ratio of 1 to 1 with respect to the rotation of the rotary knife cylinder 19. However,
the respective different diameters of the snubber support plates 129 and the knife
cylinder 19 cause the snubber support plates 129 to rotate at a reduced speed in comparison
to the knife cylinder 19.
[0056] As shown in greater detail in Figures 6, 7 and 8, with the termination of the lower,
high-speed conveyor system the individual sheets S emerge from between opposed, high-speed
belts 53 and 75. The snubber wheels 127 or 125 then strip the front portion of the
sheet from the upper, high-speed belts 75 while the rear portion of the sheet S is
still positively controlled between the opposed, high-speed belts 53 and 75. As the
sheet S continues forward and the snubber support plates 129 continue to rotate, the
sheet is pressed against the lower, low-speed belts 121 thereby decelerating the sheet.
Because the snubber wheels 125 and 127 are freely rotatable,_they are free to adapt
to the speed of the snubbed sheet S and the sheet is undamaged during its rapid deceleration.
The snubber wheels 125 and 127 may be manufactured from resiliently deformable or
compressible material, such as rubber, to further prevent damage to the sheets upon
impact of the snubber.
[0057] It is important that the actual snubbing of the sheet S occur while the tail of the
sheet S is still trapped between the opposed, high-speed belts 53 and 75. This continuous
positive control of the sheets ensures that the sheets will not become misaligned
and potentially foul or jam the system. Additionally, a deckplate (not shown) may
be positioned beneath the lower, low-speed belts to provide a solid platform against
which the snubber wheels can trap the respective sheets. Without a deckplate the snubbers
trap the sheets only against the lower, low-speed belts. Consequently, the lower,
low-speed belts 119 must be subjected to an on-going tensioning means 133 in order
to provide sufficient opposing support during snubbing. The snubber support plates
129 are timed to complete one revolution about the snubber shaft 131 in the time four
sheets are cut by the rotary knife cylinder 19, two of which will be diverted in the
previously described alternating manner to the lower delivery system 52.
[0058] The snubber assembly of the lower delivery system is driven by a gear train consisting
of a bevel gear.135, a receptive bevel gear 137, a transfer gear 139 and the snubber
shaft gear 141. The bevel gear 135, mounted on the drive shaft 35, engages the receptive
bevel gear 137 mounted on the end of the transfer axle 143. Also affixed to the transfer
axle 143 is the transfer gear 139 which drives the snubber shaft gear 141 mounted
on the snubber shaft 131. The snubber shaft 131 is rotatably mounted to the frame
12 by appropriate bearing means. The ratio of revolutions of the knife cylinder to
the snubber shaft is 1 to 1.
[0059] As best seen in Fig. 2, the lower, low-speed belts 121 traverse an idler roller 145
and a drive roller 147. The drive roller 147 is driven by a separate, variable speed
motor (not shown) by belt 148 (Fig. 4) to allow variation of the speed of the lower,
low-speed belts 121 independent of the remainder of the system. This allows the length
of overlap, when shingling the sheets, to be varied. If the lower, low-speed belts
121 were driven by the drive shaft 35, the only way to vary the length of sheet overlap
would be to change the gear ratios by physically changing the gears.
[0060] The snubber wheels 125 and 127, mounted on the snubber support plate 129, snub the
sheets against the flat belts 121 slightly before the lowest point of their rotation,
thereby decelerating the sheets. The tensioning means 133 permits adjustment of the
amount of tension on the belts 129. In the preferred embodiment depicted in Fig. 2,
the tensioning means 133 includes a tensioning roller 134 in rotational contact with
the belts 121. The belts 121 are subject to constant tensioning through the tensioning
roller 134 by the pneumatic tensioning means 136 commonly known in the art.
[0061] Once the sheet has been decelerated by the snubbers, it is now laid flat against
the lower, low-speed belts 121 and travelling at a much reduced speed. Simultaneously,
the snubber wheels 125 are lifting off the sheet and the next subsequent sheet is
emerging from between the opposed, high-speed belts 53 and 75. As seen in Fig. 8,
the snubber support plate 120 may be provided with a pair of masks 130 which act to
dampen any movement of the sheets after the snubber wheels lift off the sheet surface.
The snubber support plates 129 continue their rotation and the second snubber wheels
127 now positively guide and trap the next subsequent sheet in the same manner as
previously described. However, the next subsequent sheet, travelling at a higher speed,
is caused to overlap the previous sheet thereby achieving the desired shingling of
the sheets. The length of the overlap is determined by the speed of the lower, low-speed
belts 121. The upper snubber assembly 151, described below, operates in the same manner.
[0062] Downstream of the snubber area are a plurality of controlling rollers 153 for maintaining
alignment of the now shingled stream of sheets. The controlling rollers 153 are rotatably
mounted on the arms 155 which arms 155 are attached to the controlling roller shaft
157. In operation, the controlling rollers 153 and the arms 155 are free to follow
the height of the stream of shingled paper. Also, the controlling rollers 153 maintain
a positive control over the sheets to prevent misalignment of the sheets. Moreover,
the controlling roller shaft 157, and consequently the controlling rollers 153, are
also horizontally adjustable along the sheet path. This adjustability is important
for maintaining positive control over the sheets when sheet lengths are changed. Specifically,
before a sheet is decelerated by the snubbers, the previous and now underlying sheet
comes within the positive control of the controlling rollers 153. In this way, when
the sheet is decelerated against the previous sheet, the previous and underlying sheet
cannot become misaligned and foul the system.
[0063] The elements of the upper diverter and delivery system are functionally the same
as the corresponding elements described previously with respect to the lower diverter
and delivery system, although the elements of the upper system are not shown in detail.
Nonetheless, the upper system is easy to understand.
[0064] As a sheet emerges from between the opposed front nip rollers 21 and 23, the lower
diverter cams 45, 47 and 49 guide the sheet against the upper, high-speed belts 51
and support the sheet against the upper, high-speed belts 51 until the sheet totally
passes between the opposed upper, high-speed belts 51 and lower, high-speed belts
97 of the upper delivery section. The upper, high-speed belts 51 and the lower, high-speed
belts 97 then deliver the sheets to the snubbing area of the upper delivery system
50. The upper, high-speed belts traverse idler rollers 21, 26 and 150 and a driving
roller 152. The drive roller 152 is driven by a drive gear 154 mounted on the end
of the axle of the drive roller 152. The drive gear 154, in turn, is driven by the
drive gear 91 of the drive roller 83 of the lower delivery section 52 by means of
the interconnecting gear 92 (Fig. 3). The lower, high-speed belts traverse the idler
rollers 103 and 104 and a drive roller 117. The drive roller 117 is driven through
a gear linkage to the drive shaft 35 (not shown).
[0065] The upper snubber assembly 151, as seen in Fig. 3, is driven by the lower snubber
shaft gear 141 on the lower snubber shaft 131 through gear 159 engaging upper snubber
shaft gear 161. This allows both snubber shafts l31_and 132 to rotate at the same
ratio as the anvil cylinder 17 and the rotary knife cylinder 19. However, the snubber
shafts, being of smaller diameter, rotate slower thereby allowing the snubber wheels
to remain in longer contact with the individual sheets during deceleration.
[0066] The upper snubber assembly 151, like the lower snubber assembly 123, comprises two
rotatably mounted snubber wheels 163 and 165 rotatably mounted on the snubber support
plates 167. The lower, low-speed belts 119, against which the upper snubber system
151 traps and decelerates sheets, traverses an idler roller 169 and a drive roller
171. The drive roller 171, as with the drive roller 147 of the lower delivery system,
is driven by a variable speed motor for reasons also described previously. Similarly,
for deceleration purposes, the lower, low-speed belts 119 are subject to continuous
tensioning means 173. Additionally, a deckplate may be inserted beneath the lower,
low-speed belts, at the point the snubbers contact the lower, low-speed belts 119,
to assist in decelerating the sheets and to obviate the need for the tensioning means.
However, deck plates increase static in the system which is highly undesirable. Also,
as described in connection with the lower delivery system 52, once the sheets are
laid flat and are being shingled, a series of controlling rollers 180 maintain positive
control over the sheets as they are conveyed to the next operation.
[0067] An alternative embodiment to the present invention would add an additional pair of
opposed nip rollers downstream of the nip rollers 21 and 23 which mark the entry to
the diverting section. These additional nip rollers would be located inside the path
of the diverting cams and would be mounted on the plates 99 in the same manner as
the idler rollers 77 and 103, previously described, are presently mounted. This structure
would allow the diverter cams to rotate unobstructed. In this arrangement, both these
newly added opposed, nip rollers as well as the nip rollers 21 and 23 would be horizontally
adjustable along the conveyor path. This additional nip will act to further stabilize
and control the individual sheets as they are cut from the web by delaying the diverting
action until the sheets are held between both sets of opposed nip rollers. Additionally,
by adding the nip rollers at a position closer to the diverters, the angle at which
the individual sheets are diverted is decreased and, similarly, the stress associated
with the diverting is decreased.
[0068] While the above description only shows one embodiment of the invention, the invention
is not limited thereto since one may make modification, and other embodiments of the
principles of this invention will occur to those skilled in the art to which the invention
pertain, particularly upon considering the foregoing teachings.
1. A sheet diverter and delivery system comprising:
a first conveyor means including cutting means for cutting a continuous web into a
stream of separate sheets;
a second conveyor and third conveyor means each having an entrance and exit end, said
entrance ends being positioned after said cutting means of said first conveyor means
and said second conveyor means disposed above said third conveyor means;
a pair of diverter means for alternatively diverting the separate sheets into the
second and third conveyor means; and
means connected with each of said second and third conveyor means for decelerating
and shingling said sheets for delivering two separate streams of shingled sheets to
a subsequent printing operation.
2. A sheet diverter and delivery system as set forth in claim 1 wherein said diverter
means are a plurality of oppositely rotating diverting cams disposed adjacent the
entrance end of said second and third conveyor means.
3. A sheet diverter and delivery system as set forth in claim 1 wherein said cutting
means comprises a rotary cutting cylinder having at least one knife blade and an opposed
anvil cylinder whereby a continuous web of printed paper is run between said cutting
cylinder and anvil cylinder and cut into separate sheets.
4. A sheet handling system for receiving a moving, continuous web, cutting sheets
therefrom, and diverting alternate sheets to one of two delivery paths, comprising:
a cutting means for receiving the web and cutting the web into individual sheets,
thereby forming a stream of cut sheets;
conveyor means positioned downstream of the cutting means and defining first and second
delivery paths for receiving sheet material from the cutting means and transporting
sheets to predetermined points of delivery, the delivery paths being disposed on opposite
sides of the travel path of the sheet material leaving the cutting means and each
delivery path being at least partially defined by a conveyor system having an entry
portion and an exit portion downstream of the entry portion forming the point of delivery
for that delivery path, in each of which delivery paths a sheet is transported under
substantially continuous control from the entry portion to the exit portion; and
diverter means for alternately diverting the sheet material cut by the cutting means
to the entry portion of one of the two delivery path conveyor systems under substantially
continuous control;
the cutting means being timed so that the leading edge of the continuous web is received
by the conveyor means before the sheet is cut from the web.
5. A sheet handling system in accordance with claim 4, wherein the conveyor systems
of the delivery paths comprise closely spaced, endless conveyor belts.
6. A sheet handling system in accordance with claim 4, wherein the conveyor means
further comprises a pair of nip rollers positioned at the upstream end of the conveyor
means to receive and positively engage the leading edge of the continuous web before
the sheet is cut from the web.
7. A sheet handling system in accordance with claim 4, wherein the diverter means
comprises first and second sets of oppositely rotating diverting cams disposed on
opposite sides of the travel path of the sheet material leaving the cutting means
and received by the conveyor means, each set of diverting cams including a plurality
of similarly shaped cams fixed with respect to a common axis for rotation about the
axis and being timed with the receipt of sheet material by the conveyor means so that
the sheets are alternately diverted by the set of diverting cams from the initial
travel path of the sheet material to the entry portion of one of the two delivery
path conveyor systems under substantially continuous control.
8. A sheet handling system in accordance with claim 7, wherein at least one of the
diverting cams of each set is adjustable along its associated axis.
9. A sheet handling system in accordance with claim 4, wherein_the cutting means comprises
a rotating cutter having at least one cutting blade extending across the width of
the web and an opposed anvil member cooperating with the cutting blade to define a
cutting area, the continuous web being passed through the cutting area to the conveyor
means.
10. A sheet handling system in accordance with claim 6, wherein the nip rollers are
driven at an overspeed so that sheets cut from the web are spaced therefrom.
11. A sheet handling system in accordance with claim 4, wherein the delivery path
conveyor systems are driven at a speed such that sheets transported in each conveyor
system are spaced from each other upon arrival at the exit portion of the conveyor
system.
12. A sheet handling system in accordance with claim 4, further comprising a delivery
system for receiving sheets at the points of delivery of each delivery path conveyor
system, decelerating the sheets, and depositing the sheets on a delivery conveyor
operating at a speed less than the speed of the sheets at the point of delivery, so
that the decelerated sheets will overlap in shingled relation on the delivery conveyor.
13. A sheet handling system in accordance with claim 12, wherein each delivery system
comprises:
a conveyor system positioned downstream of the point of delivery, dropped relative
to the travel path of the stream of sheets exiting the point of delivery and having
a conveying surface facing the sheet travel path; and a snubbing means positioned
near the upstream end of the conveyor system for trapping each of the incoming sheets
against the conveying surface of the conveyor system so that each sheet-is thereby
decelerated to the speed of the conveying surface; the conveying surface being operated
at a speed less than the speed of the sheets exiting the point of delivery, and the
snubbing means being timed with respect to the arrival of the sheets so that a sheet
is trapped against the conveying surface of the conveyor system substantially as the
tail of the sheet exits the point of delivery.
14. A sheet handling system for receiving a stream of moving, regularly spaced apart
sheets from a point of delivery, decelerating the sheets, and placing the decelerated
sheets in a shingled format, comprising:
a conveyor system positioned downstream of the point of delivery, dropped relative
to the travel path of the stream of sheets exiting the point of delivery and having
a conveying surface facing the sheet travel path; and a snubbing means positioned
near the upstream end of the conveyor system for trapping each of the incoming sheets
against the conveying surface of the conveyor system so that each sheet is thereby
decelerated to the speed of the conveying surface; the conveying surface being operated
at a speed less than the speed of the sheets exiting the point of delivery, and the
snubbing means being timed with respect to the arrival of the sheets so that a sheet
is trapped against the conveying surface of the conveyor system substantially as the
tail of the sheet exits the point of delivery.
15. A sheet handling system in accordance with claim 14, wherein the snubbing means
is timed with respect to the arrival of the sheets so that a sheet is trapped against
the conveying surface of the conveyor system just before the tail of the sheet exits
the point of delivery.
16. A sheet handling system in accordance with claim 14, wherein the snubbing means
is timed with respect to the arrival of the sheets so that a sheet is trapped against
the conveying surface of the conveyor system immediately after the tail of the sheet
exits the point of delivery.
17. A sheet handling system in accordance with claim 14, wherein the point of delivery
is defined by the discharge end of a conveyor system comprising closely spaced, endless
conveyor belts.
18. A sheet handling system in accordance with claim 14, wherein the snubbing means
comprises a plurality of aligned snubbers mounted on a common axis for rotation, the
common axis being positioned substantially perpendicular to the travel path of the
incoming sheets and parallel to the conveying surface of the conveyor system.
19. A sheet handling system in accordance with claim 18, wherein each snubbing means
comprises a snubber plate rotatably mounted on a common axis, said snubber plate having
an outer perimeter mounted to which are a pair of freely rotating snubbing wheels
180° apart, and the snubbing means being timed with the arrival of the sheets so that
the snubbing wheels of a snubber alternatingly act to trap successive sheets against
the conveying surface.
20. A sheet handling system in accordance with claim 19, wherein each snubber further
comprises a trailing means for urging the portion of a trapped sheet upstream of the
snubber wheel to the conveying surface.
21. A sheet handling system in accordance with claim 14, wherein the conveyor system
comprises a plurality of laterally spaced, endless conveyor belts and the conveying
surface is the surface of the belts facing the sheet travel path.
22. A sheet handling system in accordance with claim 14, further comprising a roller
means positioned downstream of the snubbing means and resting against the conveying
surface for urging the shingled sheets transported on the conveying surface against
same.
23. A sheet handling system in accordance with claim 21, further comprising tensioning
means associated with the conveyor belts for maintaining a desired tension in the
belts.